The invention relates to an apparatus for pulling out an object, having an elongated inner lumen, from its anchorage in a body, particularly a heart pacemaker electrode or a defibrillator electrode with an electrode cable having a spiral helix. The apparatus has an anchoring part which is introduced into the inner lumen of the object and activated by an actuating device, and a tube, through which a control wire extends, which is connected to the actuating device. A relative movement between the tube and the control wire produces an axially acting force which deforms the anchoring part from a displacement configuration and to an expanded locking configuration to engage the lumen.
An apparatus is described in U.S. Pat. No. 5,632,749 which is one of the previously known embodiments and has an anchoring part constructed as a slotted sleeve, which can be activated by the relative movement between the tube and the control wire. The sleeve is slotted along its longitudinal axis and constructed in such a way that, for activating the apparatus, it can be enlarged in diameter. For this purpose, mutually facing conical surfaces are provided at the distal end of the tube as well as at the distal end of the control wire. These conical surfaces are brought into engagement with the slotted sleeve by pulling the control wire so that the slotted sleeve is expanded and, along a plurality of windings of a spiral helix, is pressed against spiral helix of an electrode cable, in order to achieve a frictional connection.
It is a disadvantage of this apparatus that, in order to achieve an adequate frictional connection, high axial forces must be exerted on the slotted sleeve pulling the control wire and holding the sleeve against the tube. It is a further disadvantage that only a relatively slight increase in the diameter of the slotted sleeve is possible. For this reason, differently dimensioned extraction devices must be kept in readiness, depending on the diameter of the inner lumen of the spiral helix of the heart pacemaker electrode or the defibrillator electrode.
A further extraction device, known from U.S. Pat. No. 5,632,749, has a flexible tube which, in the vicinity of its distal end, has several parallel divisions, which are distributed over the periphery of the flexible tube and extend axially. In this way, several strips, which are directly adjacent to one another in the circumferential direction, are formed between the divisions. The control wire of the extraction device, which is shown in FIG. 12 of U.S. Pat. No. 5,632,749, is connected with a distal end of the flexible tube. With one pull of the control wire, the front end of the flexible tube end is compressed and the strips, formed between the incisions, are deformed toward the outside and pressed against the spiral helix.
The pull-out forces achievable with this device are extremely slight, since the friction, achievable with the radially bulging strip, is limited to a very small contact area between the bulging strip and the spiral helix.
Starting out from the state of the art described above, it is an object of the invention to provide an extraction apparatus, especially an extraction apparatus for single spiral or multi-spiral heart pacemaker electrodes or defibrillator electrodes, which apparatus can be used relatively largely independently of a diameter of an inner lumen, and permits high pull-out forces to be transferred.
This objective is accomplished for an apparatus of the type described above because an anchoring part, in its locking configuration, has several radial expansions, which are offset relative to one another in the axial direction.
As a result of the radial expansions, which are offset to one another in the axial direction, a spiral helix forming a lumen is deformed by a spiral offset of adjacent spirals, so that, aside from a frictional connection between the anchoring part and the spiral helix, an interlocking connection is formed, which permits high pull-out forces. This effect is noticeable at low radial forces of the anchoring part particularly in the case of multi-spiral heart pacemaker electrodes or defibrillator electrodes.
In the case of a preferred embodiment, the anchoring part has a thin-walled metallic tube section which is provided with axially extending wall incisions, which are disposed at an axial distance from one another. Moreover, the wall incisions can be formed alternately on opposite sides of the wall of the tube. Alternatively, it is also possible for adjacent wall incisions, in the circumferential direction of the tube, to be disposed offset in each case by a quarter of the circumference of the tube.
The wall incisions can also be disposed so that easily deformable cross members remain in the radial direction between adjacent wall incisions. Moreover, the arrangement can be such that, in addition to the cross members, mutually offset in the axial direction, radially opposite cross members or several cross members along the circumferential direction, which are not offset from one another in the axial direction, are also provided.
The length of the wall incisions for producing cross members, which are or are not offset, is a multiple of the diameter of the tube, for example, three times the diameter of the tube.
The wall incisions can also be constructed as wider wall cut-outs. In particular, the wall cut-outs can extend so far into the tube casing or into the tube wall, that only a trough is left over from the original tube. If the height of this trough is significantly less than the radius of the tube, the deformability is particularly good.
In the case of an appropriate embodiment, provisions are made so that the wall cut-outs, at their axial ends, form an angle of about 30 degrees to 90 degrees and preferably of 45 degrees with the longitudinal axis of the tube.
In the case of a preferred embodiment, a distal end of the control wire is firmly connected with a distal end of the tube section forming the anchoring part. In this way, the tube section, forming the anchoring part, can be stressed not only in compression but also in tension for the purpose of deforming the anchoring part.
In the case of a different embodiment, the distal end of the control wire is provided with a stop head, which can come to rest against the distal end of the tube section forming the anchoring part. Alternatively, it is also possible to construct the distal end of the tube as a deformable tube section, which is connected in one piece with the tube, or to provide the anchoring part or the tube section as an independent part, separate or separable from the tube.